R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Reply
 
Thread Tools Search this Thread
Old 05-12-2002, 06:24 AM   #46
Tech Master
 
Alvin's Avatar
 
Join Date: Aug 2001
Location: Singapore, Jurong East
Posts: 1,654
Default

Quote:
Alvin in your 414 posts, I got a few things mixed up. Does increasing the rc in one end make that end harder to roll? And does increasing the rc in one end increase the traction of that end?
Well by raising the roll centre, it will decrease that end's ability to - in another words, the roll resistence will increase...

About the traction incresing, this is an interesting issue. A lot of ppl tell me it will increase traction.... I will disagree. A high roll centre seems to give a lot of camber change into a corner, so the rear (say the rear) will grip.... *initially* but after that the rear end of the car tends to "step out", which gives exceptional steering.... The problem I feel with this is the rear tire wear rate, it seems to be very high since the rear is sliding slightly, and not gripping and going forward...

Similarly I experience with a higher RC in the front, the car has exceptional ability to dive into the corner, and has very agressive steering but tends to understeer out of the apex. So I usually run a lower relative RC in the front, for more consistent traction level and good grip out of the corner.

Quote:
Also mcrisp pointed out that increasing the rear toe-in may work well in the first few minutes but later as the tires get warmer things become different. What's the second part of the story? Is the car going to push after the first few minutes?
Hmm I have no such problems yet - my ta04 can only run -2 degree toe in. So far given the races I've had occasion to attend and the bashing session on my home track, which we play 23T stock or mod motors for about 10 mins, the handling is more or less the same, till the batteries dump....

I believe mcrisp can shed more light here....

Over to you mcrisp sir!

Last edited by Alvin; 05-12-2002 at 06:26 AM.
Alvin is offline   Reply With Quote
Old 05-12-2002, 06:42 AM   #47
Tech Initiate
 
Join Date: Apr 2002
Posts: 38
Default

What can I fiddle around with to adjust roll center on a mr4tc?
mandy is offline   Reply With Quote
Old 05-12-2002, 06:47 AM   #48
Tech Master
 
Alvin's Avatar
 
Join Date: Aug 2001
Location: Singapore, Jurong East
Posts: 1,654
Default

mcrisp: About the front one ways. You mentioned that one ways give more steering on power. I have not done much car setups with one ways - 'cause I always experience a front differential will give me more on-power steering - won't both front wheels spinning at the same rate actually cause understeer?

The only time I have tried a front one way which doesn't understeer is a roll axis with the front rc located quite low, and the rear rc very high - I drove the setting with a differential, and it was already very nice setting (apart from tire wear). For fun then I swapped over to a dual one way, and yes I experienced even better on/off power steering, at the expense of tire wear and significantly reduced brakes.... I also stopped using this setting because while the car had exceptional steering etc.etc. the nitro cars on the track actually found it easier to overtake me! So I went back to a diff.

Also, when running a dual one way setup, is the rear of the car expected to be loose even with a front high rear low roll axis? I was told at the last Worlds in Malaysia (I didn't play rc back then) masami and hara's cars had pretty loose rear ends, but were very under control. I'm wondering if I should try to achieve a setup as such.

Hear from ya soon!

Regards,
Alvin
Alvin is offline   Reply With Quote
Old 05-12-2002, 06:49 AM   #49
Tech Master
 
Alvin's Avatar
 
Join Date: Aug 2001
Location: Singapore, Jurong East
Posts: 1,654
Default

Quote:
Originally posted by mandy
What can I fiddle around with to adjust roll center on a mr4tc?
On your shock tower, there will be (i believe) 6 holes for the camber links. These are the ones which allow you to adjust your roll centre. You need to ask the ppl in the MR4TC forum if the car has other means of adjusting the roll centre: my TA04's steering uprights are asysmetrical and can be used to make fine rc adjustments too.
Alvin is offline   Reply With Quote
Old 05-12-2002, 06:52 AM   #50
Tech Master
 
Alvin's Avatar
 
Join Date: Aug 2001
Location: Singapore, Jurong East
Posts: 1,654
Default

mcrisp: sorry yet another question! My friend's Tamiya TB-EVO 1 has a very odd stock roll centre. The front and rear ends are relatively high, for a eletric car. I have discussed this issue with a guy who deals with 1:1 scale cars, and we are unsure how the car will respond in a corner.... Only kind of track I feel it will work is a very large, flowing track....

Right now the axis is tuned so that the the front is higher than the rear, it is the best we could do as the front rc of a EVO 1 can't be changed, at least not without mods, afaik.

Thanks!
Alvin is offline   Reply With Quote
Old 05-12-2002, 07:03 AM   #51
Registered User
 
mcrisp's Avatar
 
Join Date: May 2002
Location: Toronto Canada
Posts: 68
Default

Hi Guys.

Just watching the F1 race! It is kool to see someone else out in front for a change! Go Montoya! I Hope Sato is ok...just saw the crash.

Trips:

From my experience 5mm of up-travel is too much. This can certainly contribute to a lazy turn-in because the car will role more. I would suggest that you try limiting the up-travel to 2 or 3mm. I talked to Todd Hodge briefly at the ROAR nats in California about those XXXS droop screws. They are working on a solution. I would use limiters inside the shock instead of the droop front droop screws.

Alvin & Mandy:

In general raising the roll center will decrease the traction at that end of the car because you are reducing the roll at that end of the car. Having said that, if that end of the car was already too soft, then decreasing the roll could actually increase the traction. As with a lot of adjustments if you take them to an extreme you will get the the opposite affect.

Mandy to adjust the roll center you need to make changes to the upper link or lower A arm. To raise the roll center you need to lower the inside pivot point of the upper link...or...raise the inside pivot point of the lower "A" arm. do the reverse to lower the roll center.

If the rear toe-in is too severe causing the rear tires to overheat part way through the race, this will cause an oversteer situation for the end of the race. The less traction the track has the more rear-toe in you can use without worrying about overheating.
mcrisp is offline   Reply With Quote
Old 05-12-2002, 07:24 AM   #52
Registered User
 
mcrisp's Avatar
 
Join Date: May 2002
Location: Toronto Canada
Posts: 68
Default Alvin

Hi Alvin,

When I first started thinking about front one-ways I thought the same thing that you stated in your post. I use to think that with both front wheels pulling at the same rate, the car would push more. But the opposite happens.

The TBO1 EVO does have a high RC, which means you will want to run softer springs and sway bars to get the car to roll enough to get traction.
mcrisp is offline   Reply With Quote
Old 05-12-2002, 07:30 AM   #53
Tech Master
 
Alvin's Avatar
 
Join Date: Aug 2001
Location: Singapore, Jurong East
Posts: 1,654
Default Re: Alvin

Quote:
Originally posted by mcrisp
Hi Alvin,

When I first started thinking about front one-ways I thought the same thing that you stated in your post. I use to think that with both front wheels pulling at the same rate, the car would push more. But the opposite happens.
What roll axis do you usually run for a dual one way equipped car? I sure would like to try my hands on one ways!

Thanks dude.

~Alvin
Alvin is offline   Reply With Quote
Old 05-12-2002, 07:56 AM   #54
Tech Initiate
 
Join Date: Apr 2002
Posts: 38
Default

Thanks heaps Alvin and mcrisp.

mcrisp I'm a bit surprised the overheating of the rear tires with too much rear toe-in would lead to oversteer. I really expected the car would push.
mandy is offline   Reply With Quote
Old 05-12-2002, 07:57 AM   #55
Registered User
 
mcrisp's Avatar
 
Join Date: May 2002
Location: Toronto Canada
Posts: 68
Default Roll Axis with one-ways

Hi Alvin,

I like to run the same rc at both ends of the car, so the RA is basically horizontal.
mcrisp is offline   Reply With Quote
Old 05-12-2002, 07:59 AM   #56
Registered User
 
mcrisp's Avatar
 
Join Date: May 2002
Location: Toronto Canada
Posts: 68
Default Mandy

Hi Mandy,

When tires overheat then have less traction. Thus when the rear tires overheat the rear will have less traction and cause an oversteer situation.
mcrisp is offline   Reply With Quote
Old 05-12-2002, 09:01 AM   #57
Tech Regular
 
rcruv's Avatar
 
Join Date: Jan 2002
Location: Los Angeles
Posts: 375
Default

Quote:
Originally posted by mandy
Thanks rcruv and Alvin.

If droop is measured from the ground to the bottom of the A-arm (as rcruv pointed out), could I just use a ride-height gauge to do the job?

rcruv, also which part of the bottom of the A-arm? Since there is the innermost and outtermost part. I'm sure it is more objective than just picking any part.
Oops sorry, you measure from the bottom of the chassis not the ground and the bottom of the end of A-arms.
rcruv is offline   Reply With Quote
Old 05-12-2002, 09:11 AM   #58
Tech Elite
 
Join Date: Sep 2001
Location: Newville,Pa
Posts: 2,152
Trader Rating: 7 (100%+)
Default

actually as long as you are running anything above 0 droop you can measure with your ride height guage, as long as it can measure down to 1mm. Just set the chassis flat on the table without the tires on, and measure how high the bottom of the end of the suspension arm is, that is your droop. Or just get the Associated molded guage, it's like $2, and the accuracy isn't really important as long as you always get the same measurements each time you check it.
__________________
G's RC Raceway- Best off-road track on the east coast...period!!!

Pitman for Team Dallas Austin...
IMPACTPLAYR is offline   Reply With Quote
Old 05-12-2002, 10:14 AM   #59
Tech Elite
 
Trips's Avatar
 
Join Date: Aug 2001
Location: 360 Speedway
Posts: 2,251
Trader Rating: 16 (100%+)
Default

Quote:
Originally posted by mandy
My mr4tc has no droop screws. What can I do to simulate droop screw adjustments? I really want to experiment.

Can anyone explain the terms and jargons of '4mm droop' and 'rear to front droop difference'? Is there some special gauge to measure droop or is it measured just by eyeballing?
Mandy,

You can adjust the droop on your Yok by using limiters in the shocks. You'll place spacers of various thicknesses below the pistons to limit how far the shock can extend. The limiters will get you in the ballpark, then you make fine adjustments with a turn or two of the shock eyelet at the end of the shaft. IF you look at the Yokomo setup sheets, they list the overall lengths of the shocks, this is how you control droop on that car.

As to your other question, there are several ways of describing and measuring droop. When you see the term "4mm droop" it can mean two things... It can mean that the car can be lifted 4mm from its static ride height before the wheels leave the ground, or it can mean that the bottom of the hub carrier measures 4mm on a droop guage. The two are not the same, so it's important to know which method of measurment is being used when droop is specified.

Trips
__________________
MARSHAL!!
Trips is offline   Reply With Quote
Old 05-12-2002, 10:23 AM   #60
Tech Elite
 
Trips's Avatar
 
Join Date: Aug 2001
Location: 360 Speedway
Posts: 2,251
Trader Rating: 16 (100%+)
Default

Martin,

Thanks for the reply. I'm going to go with limiters for now, until I can come up with a fix for the situation, or until Losi comes up with a fix.

By the way, you answered another puzzling question for me... what you said about rear toe and tire overheating a few posts back just made the little light bulb come on for me... Most XXX-S chassis have unequal rear toe, the outer hingepin hole in the rear hub carriers isn't equal on most that I've seen. I usually fill the hole with JB weld and re-drill the carriers on a jig, but I had to replace a set at the track and had to use them straight from the bag. The left rear tire had about a degree more toe-in than the right. Early in a run, the car would push in right turns and hook in left turns, then later as the tires warmed up it would get loose in right turns and feel fine in left turns... Now I know why.

Thanks again,
Trips
__________________
MARSHAL!!
Trips is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
Driving techniques for faster corner speeds RHCranked Electric On-Road 20 01-15-2006 06:32 PM
carpet corner speed kyracer Electric On-Road 8 01-03-2006 01:20 PM
Corner Speed mutley001 Electric On-Road 9 08-23-2005 01:46 PM
On the Corner RC-HPI R/C Photography 0 08-02-2005 11:53 PM
Corner Speed Chandler Electric On-Road 1 09-21-2004 12:03 PM



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 02:40 PM.


Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net